The present invention relates to a virtualization technique for virtualizing the use of memory areas of plural memory devices, and, more particularly, the invention relates to a method of transferring data among memory devices or in a memory device.
In a Storage Area Network (SAN), which employs a technique for connecting plural computers and plural memory devices through a network, there is a technique for virtualizing the use of memory areas of the memory devices (e.g., see “Virtualization of Disk Storage (September 2000)”, which is a technology white paper of the Evaluator Group, Inc.
There are several methods of virtualization depending upon the position between a computer and & memory device where virtualization is performed.
A first method is a method in which virtualization is performed by storage management software or volume management software in a computer in which a server application is executed.
A second method is a method in which a computer having plural interfaces connecting a memory device is placed in front of the memory device to perform virtualization, or the memory device itself performs virtualization.
A third method is a method with which virtualization is performed in a network apparatus or a management server apparatus constituting the SAN. This method is classified into an in-band method of handling a control I/O (Input/Output) and a data I/O in the same network and an out-of-band method of separately providing a network for flow of the control I/O, to handle the control I/O separately from the data I/O.